Lack of an independent relationship between age-related kidney function decline and carotid intima-media thickness in a healthy Chinese population

Background. Ageing-related decline in kidney function is an independent predictor for cardiovascular events and death. However, the underlying mechanism is not clear. The purpose of this study was to identify the associations between ageing-related decline in kidney function and carotid intima media thickness (IMT) in a healthy Chinese population with normal kidney function and with no cardiovascular disease. Methods. In cross-sectional study, we examined 852 participants (aged 30-98 years, 392 men) free from cardiovascular disease and with an estimated glomerular filtration rate (eGFR) >60 ml/min/1.73 m(2). Kidney function was estimated by using two markers: eGFR, which was evaluated by the creatinine-based Modification of Diet in Renal Disease (MDRD) Study equation, and cystatin C (CYSC) level. Participants were categorized into quartiles (I-IV) of eGFR and CYSC with quartile I representing the best kidney function (the highest eGFR quartiles and lowest CYSC). Carotid IMT was analysed using M-mode ultrasonography, and elevated carotid IMT was defined as measures above the 75th percentile of the sample distribution (0.9 mm). Results. CYSC was significantly correlated with age in both males (r = 0.441, P < 0.001) and females (r = 0.634, P < 0.001). However, eGFR was only significantly related with age in females (r = -0.173, P < 0.001). CYSC was significantly associated with elevated carotid IMT in an unadjusted model in quartiles Ill and IV; the odds ratios (95% CI) were 3.64 (2.116-6.261) and 6.407 (3.786-10.84), respectively. However, this association was significantly attenuated by age adjustment and was lost after full adjustment of age and all other confounding variables including sex, body mass index, systolic blood pressure, diastolic blood pressure, triglyceride, total cholesterol, high-density lipoprotein, low-density lipoprotein, albumin, fasting blood glucose, log C-reactive protein, log interleukin-6 and fibrinogen. No significant association was found between quartiles of eGFR and higher IMT. Conclusions. Ageing is a major factor contributing to decline in kidney function in a healthy population. There is no independent relationship between ageing-related decline in kidney function and atherosclerosis in a population with normal kidney function.